The Foreign Office has stressed that Newmark’s trip does not have government backing.

But the trip threatens to undermine government attempts to present a tough line against Assad. Former foreign office minister, Denis MacShane has tabled a parliamentary question aimed highlighting the government’s embarrassment.

MacShane said:

On the day that Bashar al-Assad’s fellow despot, Colonel Gaddafi, is indicted by the International Criminal Court it is extraordinary that a government minister turns up in Damascus to meet with the man responsible for the deaths, disappearance, torture and repression of thousands of Syrians. Did Mr Newmark discuss his trip with William Hague?

Was it authorised by the Chief Whip? Who paid for the trip? How long was he in Syria? What did he say to Bashar al-Assad? It is without precedent that a minister on the government payroll goes off to meet a man now being accused of grave crimes against his people?

If the Foreign Office did authorise this trip it should have been reported to Parliament when William Hague spoke on the region last week. If it was not authorised by the Foreign Office then who is in charge of government foreign policy and contacts with dictators with blood on their hands?

Brooks Newmark, the Conservative MP for Braintree and a government whip, held talks on Monday with the controversial leader whose brutal repression of protests has been condemned by the UK.

Foreign Secretary William Hague said that while Mr Newmark had discussed the visit with him but that he had undertaken the trip in a personal capacity.

In a letter to Douglas Alexander, his Labour shadow who had demanded an explanation of government ties to the visit, Mr Hague said Britain had maintained diplomatic ties with Syria.

“My officials met with Mr Newmark and they made clear the steps that the UK Government thinks the Syrian regime should take,” he wrote. “He agreed to reflect this in his conversation with President Assad. I believe it is important that we use all means to convey these messages directly to President Assad.”

The regime has been sharply criticised for its hardline response to protests. Hundreds have died and thousands were imprisoned as it sent in the army to crush street protests for greater freedom and democratic electioons in cities across the country.

Sana, the Syrian state news agency attempted to gain a propaganda benefit from the meeting. It reported that the pair had discussed “the recent events taking place in Syria and the advanced steps achieved in the comprehensive reform programme”

A Foreign Office spokeswoman said: “It is important that we use all means to convey the message to President Assad that he must reform or step aside.”

The US-born MP was a foreign affairs whip in opposition but now covers Business and Wales. He lists Middle East policy among his special interests and has visited Syria and nearby Lebanon many times.

Sami Khiyami, the Syrian ambassador to London, was called into the Foreign Office to be warned that reports of intimidation of British-based Syrians sympathetic to the protests by embassy staff was unacceptable.

“Any such activity would amount to a clear breach of acceptable behaviour. If such claims were substantiated, the Foreign Office would respond swiftly and appropriately,” a spokeswoman said.